This invention relates to a powder composition useful for forming an image of a liquid ink on a printing medium. The present invention is also directed to a process for the formation of an image of a liquid ink on a printing medium using the powder composition.
An ink jet printer utilizing a smooth surfaced transfer drum is known (U.S. Pat. No. 4,538,156). With this ink jet printer, an image is formed on the transfer drum by a print head assembly having a number of ink jet nozzles. Thereafter, a printing medium, e.g. paper, is brought in rolling contact with the drum to transfer the image on the drum to the printing. The above ink jet printing method has a problem because the image formed on the transfer drum is apt to spread or deform during its transference to the paper.
To cope with this problem, JP-A-62-92849 proposes evaporating a solvent (water) of the ink of an image before the transference to a paper. This method, however, adversely affects high speed printing. JP-A-H3-55283 proposes cooling an image formed on a transfer drum to increase the viscosity of the ink. This method also adversely affects high speed printing.
It is an object of the present invention to provide a powder composition useful for forming an image of a liquid ink on a printing medium using a transfer medium without causing deformation of the image.
Another object of the present invention is to provide a process for the formation of an image of a liquid ink on a printing medium using a transfer medium without causing deformation of the image.
It is a special object of the present invention to provide an ink jet printing method using a transfer medium, in which deformation of an image is prevented.
In accomplishing the foregoing objects, there is provided in accordance with one aspect of the present invention a powder composition including a powder of a modified polymer having a recurring unit containing at least one carboxyl group, the carboxyl groups of part of the recurring units being in the form of a salt with an aliphatic amine having at least 6 carbon atoms, and a powder of a surfactant.
In another aspect, the present invention provides a process for forming an image-on a printing medium, including the steps of:
(a) applying a powder composition containing a powder of a modified polymer having a recurring unit containing at least one carboxyl group over a surface of a transfer medium to form a layer of the powder, the carboxyl groups of part of the recurring units being in the form of a salt with an aliphatic amine having at least 6 carbon atoms;
(b) forming an image of a liquid ink over the layer, the powder being soluble or swellable in the liquid ink so that the viscosity of the liquid ink increases when contacted with the powder; and
(c) contacting the image on the transfer medium with the printing medium so that the image is transferred to the printing medium.